This invention relates to heat sinks and particularly to the method of making them.
Heat sinks commonly are attached to electronic devices (e.g., integrated circuits) to dissipate the heat which the devices generate during operation. In order to do this, the heat sinks are designed to have a maximum surface area, the size of which determines their heat dissipating capacity, while still occupying the smallest possible volume so that the heat sink takes up as little usable space as possible in the electronic assembly.
Most heat sinks have flat surfaces called fins to dissipate the heat, and one type of heat sink, called a "pin-fin" heat sink, comprises a matrix of separate pins that extend from a backing plate. In each case, the metal fins or pins serve as the heat-dissipating means for the heat sink. In many cases, the side of the backing plate opposite the fins or pins is adapted to be mounted or otherwise secured to the electronic device to be cooled. During operation, the heat sink may be further cooled by blowing air vertically or horizontally over and between the fins or pins.
Some heat sinks, including the pin fin types, are fabricated using conventional die casting techniques in which a reusable steel mold containing cavities that correspond to the fins or pins of the heat sink is filled with molten metal such as zinc or aluminum. After the metal has solidified, the heat sink is withdrawn from the mold and finished for use. However, it is difficult to assure that all the cavities are completely filled and the pins are correctly formed with this process to proper density.
As a result, the process limits the heights of the fins or pins, the number of pins per unit area, the density of the metal, and hence the cooling capacity of the heat sink.